Blast shield for explosive devices including linear shaped charges

ABSTRACT

An explosive apparatus particularly useful for severing a member comprising a charge of explosives for effecting fracture of the member, a shield for restricting the blast effect and for limiting the travel of blast fragments on at least one side of the member, an energy absorbing means disposed between the charge of explosive and the shield, means for securing the shield to the member and means for actuating the explosive charge.

United States Patent Vnigt, in. et al. 5] Jan. 23, 1973 [s41 BLAST SHIELD FOR EXPLOSIVE 3,248,072 4/1966 Schimmel ..102/29 HC DEVICES INCLUDING LINEAR 3,336,868 8/1967 Rush et al. ..lO2/24 HC SHAPED CHARGES Inventors: H. William Voigt, Jr., Stanhope; Joseph Gulbierz, Dover; Charles Yearwood, Hopatcong, all of NJ.

Assignee: The United States of America as represented by the Secretary of the Army Filed: Jan. 18, 1971 Appl. No.: 107,381

[52] 11.5. Ci. ..l02/24 HC [51] int. Cl ..F42b 1/02 [58] Field of Search ..l02/24 HC [56] References Cited UNITED STATES PATENTS 2,797,892 7/1957 Ryan ..l02/24 HC Primary Examiner-Verlin R. Pendegrass Att0rneyl-iarry M. Saragovitz, Edward J. Kelly and Herbert Ber] [57] ABSTRACT An explosive apparatus particularly useful for severing a member comprising a charge of explosives for effecting fracture of the member, a shield for restricting the blast effect and for limiting the travel of blast fragments on at least one side of the member, an energy absorbing means disposed between the charge of explosive and the shield, means for securing the shield to the member and means for actuating the explosive charge.

7 Claims, 4 Drawing Figures BLAST SHIELD FOR EXPLOSIVE DEVICES INCLUDING LINEAR SHAPED CHARGES The invention described herein may be manufactured, used and licensed by or for the Government or for Governmental purposes without payment to us of any royalties thereon.

BACKGROUND OF THE INVENTION This invention relates to explosive devices and in particular to explosive devices which may be used for cutting or severing members' The use of explosive charges, e. g. linear-shaped charges, both solid and liquid explosive, has become widespread to accomplish hole cutting, the severing of materials and controlled demolition.

The full capability of such explosive charges for industrial and commercial uses has not been achieved because no economically feasible and operationally satisfactory explosive device has been developed which is acceptable for use in or in proximity to areas where there may be personnel or property which is capable of damage. More specifically, the detonation of explosive charges in accomplishing a cutting or severing function causes the generation of dangerous flying fragments as well as an overpressure of blast effect, either of which is a source of possible injury to personnel or property in proximity to the blast. Attempts have been made to develop an explosive device which is shielded to guard against fragmentation and blast effect. For example, it has been proposed that in conjunction with a linearshaped charge, a relatively heavy metal shield be secured by bolts or rivets to a member to be cut or severed. This approach has been found to be unsatisfactory because it is unsuccessful in reducing the blast effect, and the securing devices, i.e., the rivets or bolts, are torn from their moorings thus becoming very dangerous projectiles and a further hazard to person and property rather than a source of safety.

SUMMARY OF THE INVENTION It is the principal object of this invention, therefore, to provide an" explosive device for use in cutting or severing a member, which device can be utilized notwithstanding the presence of personnel or property in the immediate proximity of the blast and without injury to either person or property.

This object and others not enumerated have been accomplished by the explosive apparatus of the present invention, one embodiment of which may include a charge of explosive, a shield means for restricting the blast effect and for limiting the travel of blast-resulting fragments, an energy absorbing means disposed between the charge of explosive and theshield means, means for securing the shield means to a member to be cut or severed and means for actuating the explosive charge.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the present invention may be had from the following detailed description thereof, particularly when read in the light of the accompanying drawings, wherein:

FIG. 1 is a partial elevational cross-sectional view of an aircraft structure having an explosive device according to the invention positioned for severing the aircraft structure and skin to provide an emergency exit opening as desired;

FIG. 2 is a cross-sectional perspective view through the line 2-2 of FIG. 1;

FIG. 3 is an enlarged cross-sectional view of the explosive device of the present invention mounted on the skin of an aircraft and FIG. 4 is a view similar to FIG. 3 but showing the operation of the explosive device during detonation.

DETAILED DESCRIPTION The uses of shaped charges in both industry and commerce are legion. Such charges can cut holes in members, cut slits in members, remove a section from a member to form a relatively large opening by severing, or completely sever a member to form two or more pieces. As noted above, however, the use of such shaped charges has been limited when the blast environment might present a danger to person or property.

One such prospect for shaped charges which has not been exploited because of possible injury to nearby persons has been the use of such charges to provide emergency exits in commercial passenger aircraft. To be acceptable for this function, an explosive device is required to include a light weight, high-strength shield to protect the aircraft passengers from the fragments and the overpressures or blast effect associated with the detonation of the charge.

The explosive device of the present invention, inter alia is capable of and useful for severing the air frame and skin of an aircraft to form an opening of sufficient size to permit emergency egress by passengers. Accordingly, this detailed description is directed to the explosive device of the invention used in such a manner. It is to be understood, however, that the explosive device of the invention may be used with respect to many other members and this description with respect to an aircraft is by way of explanation and not limitatron.

Referring therefore to FIG. 1, an explosive device according to the present invention is shown and designated generally by the reference numeral 10. Device 10 is shown in conjunction with a portion of an aircraft having structural members 12 and an outer skin 14. The explosive device 10 is shaped to conform and be in surface-to-surface contact with the skin and structural members of the air frame and is secured thereto by suitable rivets 16. The manner in which explosive device 10 is mounted to the aircraft air frame so as to be in surface-to-surface contact with the elements thereof is discussed below in detail.

As can be seen in FIG. 2, the explosive device 10 includes a linear-shaped charge 20 which is positioned by a molding material 22 within a generally U-shaped blast shield 24. Blast shield 24 is provided with inner and outer flanges 26 and 28 respectively, which flanges are adapted for surface-to-surface contact with the surface of a member to be severed, in this case either the structural members 12 or skin 14 of the aircraft.

The device 10 is secured to the surface of the member to be severed by rivets 1.6, it is to be noted, however, that the rivets 16 are provided only in outer flange 28. This manner of securing device 10 to the member to be severed permits the separation of the severed portion from the main portion of the member without restriction by the explosive device 10. If the explosive device is to be utilized for cutting a slit or slot wherein an opening is to be formed without the removal of material of any particular shape, explosive device may be secured to the member to be out both through inner flange 26 and outer flange 28.

Referring now to FIG. 3, the detailed construction of explosive device 10 can be better seen in this exploded view. More specifically, the explosive device 10 is shown secured to the skin 14 of an aircraft by rivets 16 which extend both through the aircraft skin and outer flange 28. The positioning of the explosive device in this manner places an explosive charge 20 in a position adjacent the surface of skin 14 where it is desired that severing occur upon detonation of the charge. The particular linear-shaped charge which has been found to be useful for forming an emergency exit in passenger aircraft is a charge of the generally kidney shape shown having an explosive concentration of grains per foot if a solid charge of explosive, or approximately grains per foot ifa liquid charge of explosive. In this regard, it will be recognized by those skilled in the art that in utilizing a liquid explosive, a tubing such as copper tubing or the like would be shaped into the kidney pattern shown and thereafter filled with a liquid explosive for use in severing as desired.

The linear-shaped charge 20 is positioned within blast shield 24 by being molded into a suitable energyabsorbing material. One energy absorbing material which has been found to be satisfactory comprises a mixture of silicone rubber and glass micro-balloons; i.e., hollow glass beads. As is discussed below in detail, this material enables the utilization of efficient manufacturing procedures.

The blast shield per se is a laminar structure comprising a plurality of plies of woven glass roving which are manufactured using a starch-oil sizing. In this regard, it has been found that an E glass woven roving manufactured with a special-oil sizing is capable of accomplishing the desired result.

The lamination is formed by applying plies of the woven roving to a desired thickness as determined by the nature of the charge to be shielded, impregnating the plies with a laminating resin such as an epoxy or polyester, and permitting the mass so formed to cure and take on a hard shape. The resultant laminar structure comprises a glass reinforced plastic laminate which has an intermediate degree of bonding which facilitates delamination in response to the exertion of high forces thereon, e.g., the forces experienced during an explosion.

The operation of the explosive device in this regard can best be seen from FIG. 4 which shows explosive device 10 during the occurrence of the detonation of linear-shaped charge. More specifically, the linearshaped charge has been detonated by the use of an electrical detonating means (not shown) which may be one of many known generally to those skilled in this art. The detonation causes the severance of skin 14 and also the generation of fragments, e. g. fragment 30, as well as a blast effect. The presence of blast shield 24 precludes fragment 30 from passing into the area of the aircraft occupied by the passengers. Furthermore, the effect of the blast is absorbed in two manners. First,

mold material 22 is crushed between explosive charge 20 and blast shield 24 which crushing absorbs some of the blast energy. Thereafter, the delamination of the material of blast shield 24 causes the absorption of sufficient blast energy to reduce the overpressure to a level which is not injurious to personnel or property in the immediate vicinity of the blast.

Tests have been conducted on explosive devices structured in accordance with the invention which have been provided with blast shields ranging in laminar thickness between 3 and-l0 plies. Depending upon the size of the charge to be detonated, each of these devices has been used successfully and has operated in accordance with the above description.

The manufacture and installation of an explosive device according to the invention is'as follows. Initially, a mold defining the shape of the surface ofa member to be severed is prepared. Thus, with respect to the example being utilized, i.e. the inner portion of an aircraft air frame, a mold is prepared which corresponds in shape and contour to the inner surface of the aircraft skin 14 and structural rib members 12. Plies of woven roving then are applied to the desired laminar thickness as determined by the nature of the charge to be shielded. The plies of roving are impregnated with a laminating material; e.g., epoxy or polyester, and the impregnated mass is subjected to a pressure sufficient to remove the excess laminating resin. The impregnated mass is than permitted to cure either at room temperature or under heated conditions as may be desired and in a manner well known to those skilled in this art.

After curing, the shield is removed from the mold. The cavity defined by the shield is filled with the uncured silicone rubber containing catalyst and hollow glass sphres or glass micro balloons. Immediately after filling the shield cavity and before curing of the mold material, a kidney-shaped tube of predetermined crosssectional area to contain an explosive which will produce a blast of the desired intensity, is positioned within the soft silicone rubber and glass mass and thereafter curing is permitted. The curing of the silicone and glass molding material causes permanent positioning of the explosive charge within the blast shield and eliminates the need for any other securing means for positioning and holding the shaped charge in place.

With the explosive device now completely formed, it is mounted on the surface of the member to be cut; i.e., the skin 14 of the aircraft and its supporting structural ribs 12, and mating holes for rivets are drilled and rivets are positioned and secured so as to secure the explosive device in proper operating position. The shaped charge is thereafter connected to a suitable detonating means such as an electrical initiator or the like and with such a connection so made the apparatus is ready for use.

As will be recognized by those skilled in the art, the above-described structure is light in weight, economical to manufacture and has been found to be completely successful in shielding passengers and property from the effect of the detonation of the linear-shaped charge in forming an emergency exit opening in the skin of an aircraft. The adaptability of the explosive device according to the invention for use in other areas, e. g. for the purpose of cutting holes or slots in metal members, is also considered to be readily recognizable by those having skill in the art.

[n this regard, it is considered to be manifest that the present invention can be altered or modified in many ways without departing from the spirit and scope thereof.

We claim:

ll. Explosive apparatus for cutting or severing a member comprising:

a shaped charge of explosive for effecting fracture of said member;

shield means comprising a progressively deformable sheet of material having an inner and an outer flange in contact with said member for restricting the blast effect and for limiting the travel of blast fragments on one side of said member;

means for rigidly securing the outer flange of said shield means to said member;

energy absorbing means disposed between said shaped charge and said shield means, said energy absorbing means comprising a mixture of silicone rubber and a crushable material selected from the group consisting of collapsible glass beads and hollow glass spheres; and

means for actuating said explosive charge.

2. Apparatus according to claim ll wherein said deformable sheet comprises a sheet of glass reinforced plastic laminate material and the progressive deformation of said sheet comprises progressive delamination.

3. Apparatus according to claim 1 wherein said explosive charge is a shaped charge, said shaped charge being rigidly secured with said mixture of silicone rubber and glass beads such as to be spaced from said shield means and adjacent said member.

4. Apparatus according to claim 1 wherein said explosive charge is a shaped charge, said shaped charge being rigidly secured within said means for absorbing such as to be spaced from said shield means and said adjacent member. v

5. Apparatus according to claim 1 wherein said shield means comprises a progressively deformable sheet of material, the progressive deformation of said progressively deformable sheet for damping the blast effect of said explosive charge and for absorbing the impact energy of said blast fragments.

6. Apparatus according to claim 5 wherein said deformable sheet comprises a sheet of glass reinforced plastic laminate material and the progressive deformation of said sheet comprises a progressive delamination.

7. Apparatus according to claim 6 wherein said explosive charge is a shaped charge, said shaped charge being rigidly secured within said mixture of silicone rubber and glass beads such as to be spaced from said shield means and said adjacent member. 

1. Explosive apparatus for cutting or severing a member comprising: a shaped charge of explosive for effecting fracture of said member; shield means comprising a progressively deformable sheet of material having an inner and an outer flange in contact with said member for restricting the blast effect and for limiting the travel of blast fragments on one side of said member; means for rigidly securing the outer flange of said shield means to said member; energy absorbing means disposed between said shaped charge and said shield means, said energy absorbing means comprising a mixture of silicone rubber and a crushable material selected from the group consisting of collapsible glass beads and hollow glass spheres; and means for actuating said explosive charge.
 2. Apparatus according to claim 1 wherein said deformable sheet comprises a sheet of glass reinforced plastic laminate material and the progressive deformation of said sheet comprises progressive delamination.
 3. Apparatus according to claim 1 wherein said explosive charge is a shaped charge, said shaped charge being rigidly secured with said mixture of silicone rubber and glass beads such as to be spaced from said shield means and adjacent said member.
 4. Apparatus according to claim 1 wherein said explosive charge is a shaped charge, said shaped charge being rigidly secured within said means for absorbing such as to be spaced from said shield means and said adjacent member.
 5. Apparatus according to claim 1 wherein said shield means comprises a progressively deformable sheet of material, the progRessive deformation of said progressively deformable sheet for damping the blast effect of said explosive charge and for absorbing the impact energy of said blast fragments.
 6. Apparatus according to claim 5 wherein said deformable sheet comprises a sheet of glass reinforced plastic laminate material and the progressive deformation of said sheet comprises a progressive delamination.
 7. Apparatus according to claim 6 wherein said explosive charge is a shaped charge, said shaped charge being rigidly secured within said mixture of silicone rubber and glass beads such as to be spaced from said shield means and said adjacent member. 